The present invention generally relates to a shaft coupling and more particularly relates to a coupling for transmitting torque from a flexible driveplate of an engine to a shaft driving a gearbox.
Mobile gantry cranes are generally known for lifting, loading, and moving heavy loads and containers. Such cranes are commonly used at shipping yards, railyards, construction sites, etc. A gantry crane typically has a frame which supports a hoisting device in an elevated manner. Particularly, the frame may include a movable trolley assembly from which wire ropes are movably suspended for lifting and lowering loads. A rotatable hoisting drum is mounted to the trolley assembly to pay out and retract the wire ropes. Also, gantry cranes are typically provided with drivable and steerable wheels so that the cranes can be driven around a site for loading.
Hydraulic power is conventionally used for operating some or all of the functions on a gantry crane. For example, hydraulic actuators, such as hydraulic motors or hydraulic cylinders are conventionally provided to drive and steer the wheels, move the trolley on the frame, and/or rotatably drive the hoisting drum. Such hydraulic motors and actuators are supplied with pressurized hydraulic fluid from a hydraulic pump.
An internal combustion engine drives the hydraulic pump via a transmission gearbox. A conventional engine has a rotating flywheel driven by the crankshaft. Various coupling assemblies are known for torsionally connecting the engine flywheel to an input of gearbox. In order to compensate for axial misalignment between the flywheel and the gearbox input pinion, it is known to secure a flexible plate to the flywheel and to mount the coupling centrally to the flexible driveplate. The flexible plate has a circular body which is circumferentially secured to the flywheel, and the body has an inner portion that is spaced from the flywheel. A coupling according to the invention is mounted to a center of the flexible driveplate to transfer torque to the gearbox input pinion. If the gearbox input pinion is axially misaligned relative to the engine flywheel, the flexible plate resiliently deforms accordingly, while still transmitting torque from the flywheel to the coupling member to drive the gearbox.
The conventional coupling includes two pieces: (a) a female spline coupling member mounted to the flexible plate, and (b) a male--male splined shaft member. One end of the conventional male--male splined shaft member is matably received in the female spline coupling member, and an opposite end of the male--male splined shaft member is matably received in the female splined hub of the gearbox input pinion. More specifically, the shaft member has oppositely-directed male splined ends which are received in respective female splined openings formed in the female coupling member and the gearbox pinion. Together, the splined connections facilitate torque transmission from the flexible driveplate to the gearbox input shaft. Additionally, both of the splined connections accommodate axial vibration or movement which may occur between the flexible plate and gearbox input pinion.
The conventional coupling with the male--male splined shaft has tended to excessively wear against the female coupling member, ultimately causing failure of the coupling. This necessitates maintenance to replace the coupling and results in undesirable down time of the crane, reducing productivity of the crane and the loading facility. On a conventional coupling assembly, the splines of the female coupling are positioned closely to the flexible drive plate. This close axial proximity subjects the female coupling member to high wear forces during deformation of the flexible driveplate. The spline coupling at the pinion, however, is positioned farther away from the driveplate in an axial direction, creating a leverage or mechanical advantage which lessens the lateral wear forces on the splines. Therefore, the spline coupling at the input pinion is subjected to a lower wear rate than the female coupling on the conventional driveplate.
It is desirable to provide an improved coupling which transmits torque from a flexible driveplate to a gearbox which has reduced wear.